It came on quickly, said assistant principal Richard Warnock, followed by rain and lightning, and “2,000 people went running for the gymnasium.”

After that year and another threat of rain the following year, the superintendent declared all future Bridgewater-Raynham graduations would be indoors. This year’s ceremony, which will take place Sunday at 1 p.m., is no exception.

“Now, we don’t even discuss it,” Warnock said. “It’s inside.”

Brockton High School, on the other hand, will have their graduation plan up in the air until hours before the ceremony is scheduled to begin on Saturday.

The largest school in Massachusetts virtually requires an outdoor graduation, said Brockton High principal Sharon Wolder, and Brockton’s is held each year at Marciano Stadium on the school grounds.

The rain date is Sunday, Wolder said, and if it rains on Sunday, the worst-case scenario is holding the ceremony on Monday evening.

Wolder said they are hoping, as always, for good weather on Saturday.

“We won’t postpone graduation until we absolutely have to,” she said.

The ceremony is scheduled to start at 2 p.m., Wolder said, and she’ll wait until 12 p.m. before making the call.

Saturday’s current forecast is for temperatures in the high 60s, with a partly cloudy sky. Sunday is supposed to be mostly cloudy and about 70 degrees.

These two days will be the biggest local graduation days of the year.

On Saturday afternoon, more than 1,000 students will graduate from Brockton High, while Bridgewater-Raynham will graduate the region’s second-largest class on Sunday.

Students from eight other schools in the area will graduate this weekend as well, including Abington High School, Middleboro High School, Oliver Ames High School in Easton, and East Bridgewater Junior-Senior High School.

Most of these graduations are planned to be held outside, but have an indoor option in case of rain.

The drawback of holding graduation inside is more limited space, but Bridgewater-Raynham is still able to give five tickets to each graduate.

Some seats are better than others, though, and Warnock said families will start arriving “far earlier than noon.”

They expect to see the first families at the school around 11 a.m., Warnock said, even though the doors won’t open until after 12 p.m.

For those who don’t want to brave the crowded gym, Bridgewater-Raynham offers the auditorium as an alternate viewing spot.

On Saturday in Brockton, assuming the weather holds, the gates to Marciano Stadium will open at 12:10 p.m., though the ceremony doesn’t begin until 2 p.m.

Wolder noted that certain items are not allowed into the stadium, including balloons, backpacks, strollers, large bags, umbrellas, tripods, fireworks, air horns, and other loud noisemakers.

“Things that are distracting or dangerous, is what it comes down to,” Wolder said.

Brockton’s graduation will be live-streamed on YouTube this year for the first time ever, beginning with the graduates’ procession at 1:45 p.m.